Paracetamol removal by photo-Fenton processes at near-neutral pH using a solar simulator: Optimization by D-optimal experimental design and toxicity evaluation

Abstract

This study discusses the degradation of paracetamol (PCT) by Fenton and photo-Fenton reactions at circumneutral pH with the aid of ferrioxalate and a solar simulator as the light source. The influence of three main operating variables: H2O2 concentration (HP), temperature (T) and radiation level (Rad) on PCT conversion was evaluated with a D-optimal design and a response surface methodology (RSM). The analysis of variance (ANOVA) revealed that Rad and T significantly affected the studied response. The model performance was satisfactory, giving low standard deviation (0.74) and good R2 and adjusted R2 values (0.9997 and 0.9993, respectively). The optimal conditions found for each radiation level were tested. The obtained PCT conversions after 90 min of reaction (75.52 %, 96.88 % and 91.50 %, respectively) were in good agreement with the predicted values (71.28 %, 96.75 % and 92.75 %, respectively). It was observed that the maximum and minimum levels of toxicity (bioluminescence inhibition of Vibrio fischeri bacteria) found in the system were closely related to the maximum and minimum concentrations observed for the reaction intermediaries (hydroquinone and 1,4-benzoquinone). In addition, it was only possible to completely reduce the toxicity of the system after 240 min of reaction when high levels of radiation were applied.